Marital status is associated with mortality and morbidity, but few studies provide data about obesity and marital status. This investigation will analyze the relationship between obesity, marital status and marital satisfaction in national data. Married people are hypothesized to be fatter and more likely to be obese than unmarried individuals. Variations in obesity among never married, married, separate divorced, and widowed individuals will be described for sex, race and age groups. Sociological, psychological, and behavioral variables, caloric intake and energy expenditure will be examined as antecedent and intervening factors in the relations between marital status and obesity. Marital satisfaction and marital problems will also be examined in relationship with obesity and weight changes to assess the relationship of obesity with the quality of marriage. Cross-sectional and longitudinal analysis will be conducted using nationally representative data sets, comparing the results from each data source with others in five phases. Phase I will analyze marital status and obesity in the National Survey of Personal Health Practices and Consequences (NSPHPC) collected in 1979 and 1980 on 3,025 adults. Phase II will analyze the 1971-5 cross-sectional National Health and Nutrition Examination Survey (NHANES I) and its augmentation survey, which together include a sample of 16,190 adults. Phase III will analyze the 1976-1980 cross-sectional NHANES II data on 11,864 adult comparing results with NHANES I and NSPHPC findings. Phase IV will analyze longitudinal aspects of the NSPHPC data, and the 10 year followup data from the 1982-4 NHANES I Epidemiological Followup Survey of 10,523 adults exam in NHANES 1. This longitudinal analysis will provide evidence about the direction the obesity-marital status relationship. Phase V will analyze marital satisfaction and obesity in the NSPHPC data, examining quality of marriage and obesity. This will be the first study of marital status and obesity on national samples of the United States population. Results will assist in understanding obesity, its prevention, and its management.